Overview
ISO 18417:2017 specifies a laboratory method to define a sorption capacity index for iodine charcoal sorbents used in nuclear contexts. The standard applies to granulated and crushed activated‑charcoal sorbents intended to trap gaseous radioiodine (notably radioactive methyl iodide) in nuclear power plants, research reactors, laboratories (including nuclear medicine) and sampling equipment. ISO 18417:2017 helps manufacturers and operators measure and compare the actual performance of iodine sorbents for retention of radioiodine under controlled test conditions.
Key topics and technical requirements
- Scope and applicability: Covers iodine sorbents based on activated charcoal and defines the laboratory procedure to determine the sorption capacity index.
- Test principle: Uses a carrier air stream with controlled humidity and temperature; radioactive methyl iodide (CH3I) is injected and passed through sectional sorbent columns; activity distribution is measured to derive the index.
- Sample preparation and installation cleaning: Removal of aerosols, volatile impurities and humidity prior to testing (e.g., dehumidifier and charcoal regeneration; example heating regimes are provided for zeolite and activated carbon).
- Definitions important for testing: free volume, contact time (transit time through sorbent free volume), bulk density, mass transfer zone and sorption capacity index.
- Measurement and instrumentation: Use of aerosol filters, dehumidifiers, methyl iodide generator, sectional columns, protection column and gamma monitors (for 0.364 MeV 131I) to record activity profiles.
- Calculation and reporting: Sorption capacity index is calculated per Clause 9; the standard includes test performance, uncertainty considerations and template formats for test reports (Annexes A–C).
- Test limitations: The sorption capacity index is specific to the chemical form tested (document focuses on radioactive methyl iodide) and cannot be directly compared between different iodine species.
Practical applications
- Quality control and acceptance testing of iodine charcoal sorbents and filters.
- Comparative performance evaluation of different sorbent products under defined laboratory conditions.
- Support for design and sizing of iodine retention systems in ventilation and off‑gas systems.
- Verification testing for operators, procurement specifications, and radiological protection assessments.
Who should use ISO 18417:2017
- Sorbent and filter manufacturers seeking objective performance metrics.
- Nuclear facility operators and radiological protection teams validating iodine retention systems.
- Laboratory personnel performing sorbent characterization and sampling equipment testing.
- Regulatory and quality assurance specialists needing standardized test data for audits and procurement.
Related standards and context
ISO 18417:2017 was prepared by ISO/TC 85 (Nuclear energy, nuclear technologies and radiological protection). It complements other standards and guidance on radiological protection, sorbent testing and air monitoring used in nuclear facilities.